1. Technical Field of the Invention
The present invention relates to a liquid crystal display, a manufacturing method thereof, and an electronic appliance.
2. Description of the Related Art
Hitherto, so-called transflective liquid crystal displays have been used, which can, as required, switch between the reflective display mode in which the external light including natural light and artificial indoor light is incident from the obverse side and reflected to achieve the display, and the transmissive display mode in which light from a light source is incident from the back side to achieve the display.
FIG. 9 is a cross-sectional view schematically representing the configuration of the above transflective liquid crystal display. As shown in the figure, the transflective liquid crystal display substantially comprises a front substrate 501 and a back substrate 502, a liquid crystal 503 sealed in the space between these substrates, a light guide plate 505 to guide the light emitted from a light source 504 to the entire back substrate 502, and a transflector 506 interposed between the light guide plate 505 and the back substrate 502. The transflector 506 is a sheet with pearl pigment beads diffused in a resin which was disclosed in, for example, Japanese Unexamined Patent Application Publication No. 55-84975, and has the characteristic that a part of the incident light is reflected thereby; while the remaining part is transmitted therethrough. A polarizer 507 is bonded on the outer side (the side opposite to the liquid crystal 503) of the front substrate 501, and a color filter 508, a transparent electrode 509, etc. are formed on the inner side thereof. On the other hand, a polarizer 510 is bonded on the outer side (the side opposite to the liquid crystal 503) of the back substrate 502, and a transparent electrode 511, etc. is formed on the inner side thereof.
In such a configuration, during reflective display mode, the external light such as the sunlight and artificial indoor light is incident from the front substrate 501 side, is transmitted via the polarizer 507xe2x86x92the front substrate 501xe2x86x92the color filter 508xe2x86x92the transparent electrode 509xe2x86x92the liquid crystal 503xe2x86x92the transparent electrode 511xe2x86x92the back substrate 502xe2x86x92the polarizer 510xe2x86x92the transflector 506, is reflected by the transflector 506, is transmitted along the same path in the reverse direction, and is then emitted from the front substrate 501 side, and observed by a user.
On the other hand, during transmissive display mode, the light emitted from the light source 504 is guided to the entire panel by the light guide plate 505, a part of the light is transmitted through the transflector 506 and emitted from the front substrate 501 side via the polarizer 510xe2x86x92the back substrate 502xe2x86x92the transparent electrode 511xe2x86x92the liquid crystal 503xe2x86x92the transparent electrode 509xe2x86x92the color filter 508xe2x86x92the front substrate 501xe2x86x92the polarizer 507, and is observed by the user.
As described above, during reflective display mode, the light observed by the user (hereinafter, simply referred to as the xe2x80x9cemitted lightxe2x80x9d) is transmitted through the color filter 508 twice. On the other hand, during transmissive display mode, the emitted light is transmitted through the color filter 508 only once. Assuming that the intensity of the light incident from the front substrate 501 is equal to the intensity of the light irradiated from the light source at the back substrate 502, the color purity (the degree of coloring of the light) of the emitted light during transmissive display mode is substantially one half of the color purity of the emitted light during reflective display mode. If the color purity of the color filter 508 is improved, the color purity of the emitted light during transmissive display mode can be improved; however, under such conditions, a problem of reduced brightness during reflective display mode occurs. Thus, in the conventional transflective liquid crystal display, there is a problem in that color reproducibility during reflective display mode cannot be set to be the same as the color reproducibility during transmissive display mode.
Accordingly, the present invention has been made in light of the above problems, and an object of the present invention is to provide a liquid crystal display which can set the color reproducibility during reflective display mode to be the same as the color reproducibility during transmissive display mode, a manufacturing method thereof, and an electronic appliance.
In the present invention, there is provided a liquid crystal display having a liquid crystal held between a first substrate and a second substrate comprising a plurality of spacer units which are formed on a surface of the second substrate facing the first substrate and which have apertures, a plurality of reflectors which are formed on a surface of each of the spacer units, which reflect light transmitted through the first substrate, and which have apertures corresponding to the apertures of the spacer units, and a plurality of color filters having flat portions formed on a surface of each of the reflectors and a projected portion reaching the second substrate through the apertures in each reflector and each spacer unit.
Also in the present invention, there is provided a liquid crystal display having a liquid crystal held between a first substrate and a second substrate comprising a plurality of reflectors reflecting light transmitted through the first substrate which are formed on a surface of the second substrate facing the first substrate and which have apertures, a plurality of spacer units which are formed on a surface of each of the reflectors and have apertures corresponding to the apertures in the reflectors, and a plurality of color filters having a flat portion formed on a surface of each of the spacer units and a projected portion reaching the second substrate through the apertures in each of the reflectors and each of the spacer units.
In the present invention, during reflective display mode, the light incident from the first substrate is emitted after being transmitted through the flat portion of the color filter twice, and thus, the color reproducibility during reflective display mode is dependent on the thickness of the flat portion of the color filter. On the other hand, during transmissive display mode, the light irradiated from a light source (a backlight) is incident from the second substrate side, and emitted after being transmitted through the projected portion and the flat portion of the color filter, i.e., the apertures in the spacer unit and the reflector, and thus, the color reproducibility during transmissive display mode is dependent on the thickness of the projected portion and the flat portion of the color filter. Thus, the color reproducibility during reflective display mode and the color reproducibility during transmissive display mode can be independently set by individually selecting a thickness of the flat portion of the color filter and a thickness of the projected portion. Therefore, the color reproducibility during reflective display mode can be set to be the same as the color reproducibility during transmissive display mode.
The desired color reproducibility during transmissive display mode can be realized by adjusting a thickness of the projected portion, and a thickness of the projected portion can be easily adjusted by adjusting the thickness of the spacer unit. Even when the projected portion must be relatively thick in order to obtain the desired color reproducibility during transmissive display mode, there is an advantage in that the thickness of the projected portion sufficient for obtaining the desired color reproducibility can be ensured by forming the spacer unit of a predetermined thickness.
The second substrate may have a groove corresponding to each of the apertures, and the projected portion of the color filter may reach a bottom portion of the groove through the apertures in each of the reflectors and each of the spacer units. The projected portion can be formed thicker by the depth of the groove in addition to the thickness of the reflector and the spacer unit. Thus, even when the projected portion must be relatively thick in order to obtain the desired color reproducibility during reflective display mode, the spacer unit need not be formed thicker, and the increase in thickness of the liquid crystal display can be avoided.
In the present invention, there is provided a manufacturing method of a liquid crystal display having a liquid crystal held between a first substrate and a second substrate comprising: a spacer-unit forming step of forming a plurality of spacer units on a surface of the second substrate facing the first substrate, a reflector forming step of forming a reflector to reflect light transmitted through the first substrate on a surface of each of the spacer units, an aperture forming step of forming an aperture through each of the spacer units and the reflector formed on a surface of the spacer unit, and a color-filter forming step of forming a color filter having a flat portion located on the surface of each of the reflectors and a projected portion reaching the second substrate through the apertures in each of the reflectors and each of the spacer units.
In the present invention, there is provided a manufacturing method of a liquid crystal display having a liquid crystal held between a first substrate and a second substrate comprising: a reflector forming step of forming a plurality of reflectors to reflect light transmitted through the first substrate on the surface of the second substrate facing the first substrate, a spacer-unit forming step of forming a spacer unit on the surface of each of the reflectors, an aperture forming step of forming an aperture through each of the reflectors and the spacer unit formed on the surface of the reflectors, and a color-filter forming step of forming a color filter having a flat portion located on the surface of each of the pacer units and a projected portion reaching the second substrate through the apertures in each of the reflector and each of the spacer units.
The liquid crystal display manufactured by the liquid crystal display manufacturing method has an advantage in that the color reproducibility during reflective display mode and the color reproducibility during transmissive display mode can be independently optimized by individually selecting a thickness of the flat portion of the color filter and a thickness of the projected portion.
In addition, the liquid crystal display in accordance with the present invention has an advantage in that a thickness of the projected portion sufficient for obtaining a desired color reproducibility can be ensured by forming the spacer unit of a predetermined thickness even when the projected portion must be relatively thick in order to obtain a desired color reproducibility during reflective display mode.
The aperture forming step may comprise a step of forming apertures in the spacer units and a step of forming apertures in the reflectors.
The liquid crystal display manufacturing method may comprise a groove forming step of forming a groove corresponding to each aperture on a surface of the second substrate facing the first substrate, and, in the color filter forming step, a color filter having the flat portion and the projected portion reaching a bottom portion of the groove through the apertures in the reflector and the spacer unit may be formed. In the thus manufactured liquid crystal display, the thickness of the projected portion can be increased by the depth of the groove in addition to the thickness of the reflector and the spacer unit. Thus, even when the projected portion must be relatively thick in order to obtain the desired color reproducibility during reflective display mode, the spacer unit need not be so thick, and the increase in thickness of the liquid crystal display can be avoided.
Further, there is provided an electronic appliance comprising the liquid crystal display in the first or second aspect of the present invention as a display unit. This electronic appliance has an advantage in that the color reproducibility during reflective display mode and the color reproducibility during transmissive display mode can be independently optimized.